The present invention relates to a seat belt retractor, which comprises a first emergency locking means for locking a reel shaft where a seat belt is wound up when acceleration higher than a predetermined value is applied on an vehicle, and a second emergency locking means for locking the seat belt itself.
As one of conventional type seat belt retractors, there is a seat belt retractor as shown in FIG. 12.
As it is evident from FIG. 12, this seat belt retractor is provided with a reel shaft 102, on which a seat belt 101 is wound up, and with a ratchet wheel 103, which is coaxially and integrally mounted on said reel shaft. Also, the seat belt retractor is provided with a first emergency locking means 105 for locking the reel shaft 102 by engaging an stop member 104 with the ratchet wheel 103 and a second emergency locking means 110 for locking the seat belt 101 pulled out from the reel shaft 102 by squeezing the seat belt between a sliding-squeezing member 109 and a clamp member 107, which will be described below. The second emergency locking means 110 is provided with a rotating-squeezing member 108, one end of which is rotatably mounted on a case 106 and a clamp member 107 thereof is mounted on a squeezing end of the seat belt 101, and it is further provided with the sliding-squeezing member 109, which is positioned face-to-face to the rotating-squeezing member 108 and is slidably mounted on the case 106. On each of squeezing surfaces of the clamp member 107 and the sliding-squeezing member 109 to the seat belt 101, squeezing sectors 107a and 109a are formed in smooth and irregular shapes in directions crossing transversely the directions to wind up or pull out the seat belt 101.
By such seat belt retractor provided with the first and the second emergency locking means 105 and 110, it is possible not only to lock the reel shaft 102, but also to lock the seat belt 101 itself Thus, the reliability can be extensively increased.
Meanwhile, when the second emergency locking means 110 is operated in an emergency such as vehicle collision and the seat belt 101 is locked, very strong force may be applied on the squeezed seat belt 101 in some cases.
That is, when the seat belt 101 is squeezed in normal operation of the second emergency locking means 110, the seat belt 101 is squeezed and locked as the rotating-squeezing member 108 is rotated up to a position given by 108' in a direction of the arrow D.sub.1. In some cases, however, a strong force may be applied to pull out the seat belt further beyond the normal squeezing state of the seat belt held by the rotating-squeezing member 108 and the sliding-squeezing member 109
In such case, lower end of the clamping member 107 of the rotating-squeezing member 108 bites into the seat belt 101 and squeezes the seat belt 101 with stronger force. As the result, strong force is concentrated on a squeezed portion of the seat belt 101